If you access your wordpress site or access wp-admin but see blank screen, your wordpress site will not functional. The reason of this issue is vary. Typically, your installed theme do not compatible with your wordpress version or you do not use standard wordpress theme which have some bug.
1. The first troubleshoot the code you should open WP_DEBUG in wp-config.php to ‘true’ to see what file have problem. If you have a clue, try to fix that
2. If you still cannot solve this problem, backup your wordpress file (for sure).
2.1 Go to phpmyadmin -> select your database -> select wp_options table
2.2 Find 3 records by option_name (current_theme, template, stylesheet) and edit these 3 options back to default theme (twentyten OR twentyeleven depend on your wordpress version)
2.3 Try to delete other themes file (except default theme) in file manager or ftp.
2.4 Access your website again, it should fine now but with default theme.
3. If you still have problem, try to install fresh wordpress file
3.1 Go to file manager and delete all wordpress file except wp-config.php and .htaccess
3.2 Upload fresh wordpress file and extract them.
3.3 try to access your website again
If you did all above troubleshooting guide but still having problem, feel free to contact us. We will investigate your issue and try our best to bring your site back.